The present invention relates generally, as indicated, to an inspection device and method using the same, and, more particularly, to an inspection device and method that facilitate obtaining a view of a device and/or area that ordinarily is difficult to access.
Many electronic printed circuit boards (PCB) manufactured which utilize current technology use surface mounted components. That is, the components are soldered directly to metal pads or areas on the surface of the board to make electrical connections between the component and circuits on the board and to secure the component to the board. This is contrasted with techniques in which elongate leads of the component are soldered into plated metal holes going through the board. Soldering components directly to the PCB surface is known as surface mounted technology (SMT). The term xe2x80x9ccomponentxe2x80x9d is broadly construed here as, for example, an integrated circuit, integrated circuit component, integrated circuit package, electronic component, and/or other devices, and these and other various terms used herein for components or equivalent devices are intended to be inclusive of various components with which the present invention may be used.
Many SMT components have leads that are located underneath the component package. One example is components referred to as plated leaded chip carriers (PLCC). Another example uses as the leads balls on the bottom of the component that are soldered to conductive pads or receptacle areas, e.g., concave areas, of a circuit board; such arrangement of balls and this type of connection technique sometimes is referred to as a ball grid array (BGA).
It is desirable to be able to inspect connections between such electronic components and the like and the board to which they are attached. For example, inspection may be used to verify proper connections, to find faults, e.g., an open circuit or a short circuit, and in some cases it may be possible while using a view obtained during an inspection to repair a discovered fault. Viewing and inspection may be used to see whether the connection procedure appears to have been carried out correctly and/or for other purposes.
The problem of looking at surface mounted components has been addressed in the past by using a number of instruments such as direct video viewing binocular microscopy and bore scopes. With the advent of more complex integrated circuits or like packages it has become more difficult to inspect the leads on many packages primarily because the leads are connected to the board underneath the electronic packages. This makes it even more difficult to see a desired view even by rotating the package vertically.
An apparatus and method for viewing a workpiece or the like is disclosed in copending U.S. patent application Ser. No. 09/114,987, filed Jul. 14, 1998, the entire disclosure of which is hereby incorporated by reference. Such apparatus and method use a camera to obtain an image of a workpiece and for displaying an enlarged image for viewing. Such apparatus includes techniques for aligning the camera and/or associated optics to obtain a desired view. An exemplary use of such apparatus and method include viewing and inspecting the connections between leads of an electrical or electronic component and a printed circuit board and in some cases facilitating the viewing of a faulty connection while that connection is being repaired and/or after a repair has been made.
However, it is difficult to view the leads and connections of leads of SMT components, such as a PLCC or a BGA of an integrated circuit component or package, mounted on a circuit board. These leads and connections cannot be viewed for inspection from the straight vertical because the leads are beneath the component and are not usually exposed at a side edge thereof. To view such leads and connections the board must be tilted at extreme angles for inspection. Additionally, SMT components are very small and must be viewed at some level of magnification to insure proper inspection for defects. This can be very difficult as higher level magnification inspection products, such as microscopes and video cameras, reduce working distance and make PCB manipulation for proper focus beneath the magnifier almost an art form. Although magnification instruments can be tilted to locate the SMT device within the field of view, accurate alignment and refocusing usually are required and make the process laborious. Additionally, although it is desirable to obtain a view looking in a direction parallel to the plane of the circuit board to view the complete edge solder ball(s) of a BGA device, PLCC device or similar device in which the connections are somewhat hidden, this usually is not possible even with tilting instruments which are able to be tilted to a direction that is 90 degrees to a direct view looking down at the top of the board, because other PCB components usually obstruct the view.
As a result expensive top down X-ray or ultrasonic analysis is often employed when inspecting these packages. Although X-ray or ultrasonic analysis is required to detect solder voids beneath interior balls in BGA packages, there is a need for a cost effective right angle viewing device that will detect common problems such as lead misalignment and solder shorts between leads and solder balls. Although the device will not eliminate the need for X-ray for solder voids, it will avoid a need to use expensive X-ray to find visible defects.
Because of their design and height restrictions mirrors, such as dental mirrors and other right angle mirrors, are difficult to use to view the SMT packages mounted on circuit boards, such as PLCCs and BGAs. Usually there is minimum space to place a dental mirror type device, for example. Also, it is difficult to align such a relatively large mirror type device. Additionally, if space were available for use of a dental mirror or the like, such mirrors would only obtain a limited view, for example, a view of the upper versus the lower part of the package, which is soldered to the board. Further, such mirrors can be relatively heavy and have a relatively large footprint, and, therefore, if it were to engage the circuit board, it could easily damage the board (including, for example, the board itself, conductive traces, coatings, solder connections, components, etc.).
Dental mirrors and other relatively large mirrors are difficult to manipulate accurately in close spaces to obtain a full view of, for example, solder connections under a BGA SMT component, solder connections thereof, etc., as well as of the surfaces of the component facing the board and the surface of the board facing the component. Further, it is difficult to obtain suitable lighting to illuminate the viewed area.
It will be appreciated that there is a strong need in the art to view relatively small objects and/or to view such objects where there is relatively small clearance to obtain the view.
It also will be appreciated that there is a strong need in the art to improve the viewing and inspecting of electrical and electronic components or the like and their connection or attachment to a circuit board or the like, especially in small or tight spaces.
According to an aspect of the present invention a viewing device for viewing a relatively inaccessible gap area between two closely positioned surfaces including a first reflector for reflecting a first view of at least part of a first gap area to a first relatively accessible location, a second reflector for reflecting a second view of at least part of a second gap area to a second relatively accessible location, and a support connecting the first and second reflectors together. In several exemplary embodiments, for example, reflectors can be right angle prisms and the reflectors can reflect the light by total internal reflection or by another reflection technique, such as surface reflection, reflection by a coating, dielectric mirror, etc.
According to another aspect of the present invention, a viewing device for viewing a relatively inaccessible gap area between two closely positioned surfaces including a reflector for reflecting a view of at least part of the gap area to a relatively accessible location, and a support supporting the reflector in a stable position relative to the gap area to obtain the view. In several exemplary embodiments, for example, reflectors can be right angle prisms and the reflectors can reflect the light by total internal reflection or by another reflection technique, such as surface reflection, reflection by a coating, dielectric mirror, etc.
According to another aspect of the present invention a viewing device for viewing a relatively inaccessible gap area between two closely positioned surfaces including a first reflector for reflecting a first view of at least part of a first gap area to a relatively accessible location, a second reflector for reflecting a second view of at least part of a second gap area to a second relatively accessible location, and a support connecting the first and second reflectors together, wherein the support is scored along the center to facilitate separation of the support into first and second support portions, the support portions each including a threaded post hole for use with a threaded post.
According to another aspect of the present invention a method of viewing a relatively inaccessible gap area between two closely positioned surfaces including placing a reflector adjacent relatively inaccessible gap area to view the gap from a relatively accessible location, and supporting the reflector from at least two locations to stably maintain the reflector relative to the gap area.
According to another aspect the method further includes adjusting a threaded post position the reflector to view the gap area. The adjusting of the threaded post may be performed electronically and may be controlled according to the view of the electronic viewing device.
According to another aspect of the present invention a method of making a pair of devices for viewing a relatively inaccessible gap area between two closely positioned surfaces includes forming a structure having a pair of reflectors for connecting a support, breaking the support into two pieces, and adding a threaded post to each of the two pieces of the support.
According to an aspect of the present invention a prism optically relays an angular view of a surface mounted feature.
According to another aspect a right angle prism optically relays a 90 degree view of a surface mounted feature.
According to another aspect a right angle prism is provided for optically relaying a 90 degree view of a surface mounted feature, the optical relay causing the image to be inverted so the view will be from the surface of the PCB upward facilitating viewing of the most critical solder joint of, for example, an SMT connection.
According to another aspect different axial length prism devices can be used to relay images of several SMT leads and connections and even of entire rows of leads and connections for viewing at a time.
According to another aspect the invention permits light to be projected beneath packages and turned at an angle, for example, a right angle or other angle, through the prism so that solder or other blockages may be detected beneath an SMT device connected to a circuit board.
According to another aspect a device is provided to relay a view of an object, such as an SMT device and/or its connection to a circuit board, the device being of relatively light weight and having a small footprint where it may engage the circuit board, thereby to minimize the possibility of damaging the circuit board or components thereon during use to obtain the view.
According to another aspect a support is provided for a prism device used to relay an image of SMT connections between an SMT device and a circuit board and/or for a prism device used to illuminate such SMT connections.
According to an aspect of the present invention a right angle prism is provided to optically relay a 90 degree view of one or more surface mounted features. The image presented will be from the surface of the PCB upward so that the most critical solder joint can be seen because the view is inverted. Additionally, different length prism devices can be positioned so that entire rows of leads can be viewed at a time. Another feature of this invention permits light to be projected beneath packages and turned at right angles through the prism so that solder or other blockages may be detected.
According to an aspect of the invention a new method of and apparatus for examining electronic packages or components at right angles so that leads may be inspected underneath the packages or components are provided. A right angle prism is mounted so that reflected light from the package can be seen from above or alternatively using a second right angle prism light can be introduced into that prism and viewed on the other side of the package through the other prism. This allows any viewing device to be used above the print circuit board on which the package or component is mounted to see (obtain a view) horizontal to the board. This overcomes the inability to illuminate and to see and inspect even with relatively high density arrangement of components on most boards. The device can be placed on the board at the component to be inspected and the device allows on to see under the component without expensive fiber optics or other complicated devices such as endoscopes.
According to another aspect, undesired light collection and/or reflection by one or both prisms is reduced or eliminated by light absorption or light scattering, e.g., using a light absorber or light scatterer.
According to another aspect, one or both mentioned prisms may be mounted on a bar or other support which allows the device to be placed on a printed circuit board while bridging the component or package to be examined. The bridge can either be permanently affixed so as to give a fixed distance and precise alignment or it can be a variable width so as to be adjustable for any package. A further advantage to this type of device is its ease of manufacture and its low-cost in volume production. A device of this type could be placed on a print circuit board at critical points during manufacture and left in place to provide later inspection in critical manufactured parts.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.